This was an incredibly scenic and enjoyable route, full of multicolored sheep, flowers, and sets from recent Star Wars movies. Attempting it in peak season without a tent or reservations is probably inadvisable - better to head for the mountains of Bulgaria.
For the most part, perfect. The last day was a bit too sunny, but typically, it was a cloudy 65 with a gentle sea breeze. It rained heavily one night but only drizzled momentarily during daylight hours.
There were some short stretches of exceptionally muddy cow pasture, and the last day was almost entirely beach walking. There were several steep hills and Mount Brandon offered an extended climb. Road-walking in Ireland is terrifying, since roads are rarely more than one lane wide, but these sections were limited, and drivers were fairly considerate. For the most part, the route was pleasant and fast.
Several times, when I looked on Booking and AirBnb, I didn't see a single place on the whole of the peninsula, or the only options were $150+. HostelWorld proved surprisingly useful. And I was able to pick up a few spots from cancellations and emailing around. One of the days, I walked 42 miles to reach the next available bed.
There are many pubs, restaurants, and groceries along the route. But most of them don't bother opening or serving food most of the time. I saw multiple "staff has gone fishing" signs. It pays to stock up on non-perishables. Or you could survive on the thousands of blackberries. When you do find a restaurant, mains tend to be around $15 and pints from local brewers run about $6. There's always a curry option.
I think I drank like half a liter a day and never had to fill up. But any village would likely give you water. There's likely plenty of sheep poop in the surface water.
I ended up in Ireland because the flights are consistently very cheap, both from the continent and back to the States. Once you're there, there's an impressive network of trains and buses, which all have wifi and power outlets. It can be worthwhile to purchase the tickets ahead of time, as they can be double the price at the station. Tralee is well-connected and it's possible to bail from most towns along the route.
Day 1, Tralee to Annascaul, www.strava.com/activities/7582132022
Day 2, Annascaul to Dingle Town, www.strava.com/activities/7587247760
Day 3, Dingle Town to Cloghane, www.strava.com/activities/7594156363
Day 4, Cloghane to Camp, www.strava.com/activities/7599602304